The weighing of heavy vehicles, such as cargo carrying trucks, presents a number of unique scale design problems. For example, a conventional truck scale is normally an outdoor installation which is exposed not only to the elements, but also to weights of substantial magnitude, shock caused by heavy moving vehicles engaging the scale deck, and the infiltration of abrasive chemicals, such as road salts, commonly found in a highway environment. In fact, a truck scale deck, which bridges an underlying scale pit, is subjected to a concentration of the sam e forces which cause the deterioration of highway surfaces that are supported by solid beds.
In the past, truck scales have been designed with heavy scale beams mounted in pits which were bridged by massive deck structures adapted to withstand the weight of loaded trucks while providing some protection to the underlying scale mechanism. The sheer mass involved in these assemblies required that the components of both the scale mechanism and the scale deck be individually shipped to the scale site where the scale was actually assembled on site from these components.
With the advent of electronic load cells capable of operation under the loads to which a truck scale is subjected, scale pits became shallower and much of the massive scale mechanism previously mounted within the pit was eliminated. This reduced the volume of heavy components shipped to the scale site as well as the time required to build a truck scale at the site, but the requirement for a massive scale deck was not reduced. In fact, forming these heavy decks on site and adapting them for effective mounting on load cells rather than supporting weigh beams created additional problems to be solved.
As cargo carrying highway trucks have become longer and designed to provide a greater cargo carrying capacity, truck scale decks have likewise been developed to provide enhanced strength and shock resistance. Many steel and concrete truck scale decks are supported on massive spaced beams which extend beneath each deck section. More recently with concrete decks, profiled metal sheets with "V"-shaped corrugations which extend transversely under the deck have been provided to receive the concrete, as illustrated by U.S. Pat. No. 4,392,537 to Lundborg. To further increase the strength of these structures, the corrugated bottom surface which engages the concrete of the deck has been formed with anchors which extend into the concrete as illustrated by U.S. Pat. No. 4,529,051 to Stolz et al. Although these corrugated support units which provide a bottom structure into which concrete is poured enhance the overall strength of the resultant concrete deck, they do little to simplify the problems involved in fabricating the deck on site and then mounting a massive deck structure on supporting load cells.
Ideally, it would be desirable to prefabricate completed relatively lightweight metal or concrete deck sections designed to mate with an underlying load cell assembly which interlock to form an elongate scale deck, and to then ship these preformed sections to a scale site for assembly. To make this feasible, the sections would need to be sufficiently light so that shipping costs would not be prohibitive, and yet sufficiently strong to withstand the rigors of a truck scale environment. For a concrete deck scale, the concrete deck could only be a few inches thick if shipping is to be economically feasible, and yet this deck must be sufficiently dense and strong to preclude the infiltration of road salts and moisture. The necessity to meet these requirements has, to this point, precluded the prefabrication of steel and concrete truck scale decks with their underlying support structures and economic feasibility has mandated that these decks be poured and/or built at a scale site. This is a time consuming process which requires the presence of a number of trained personnel at the scale site.